Computer memory, oftentimes referred to as main memory, primary storage, or simply memory, is computer hardware that stores information for immediate use in a computer. For example, random-access memory (RAM) is a type of computer memory implemented with semiconductor technology on integrated circuits that operates at a higher speed than secondary storage forms such as hard disk drives. Types of RAM include static random-access memory (SRAM) and dynamic random-access memory (DRAM). SRAM, oftentimes used as central processing unit (CPU) cache memory, is typically faster than DRAM but consumes more energy and offers lower memory area density than DRAM. RAM is usually organized as addressable arrays of memory cells, with each memory cell storing one bit (0 or 1) of information.